The field of this invention relates to novel homopolyoxadiazoles soluble in organic solvents such as n-cresol and useful as coatings, molded objects, films and fibers.
In the prior art, the article by Y. Iwakura, et al., in The Journal of Polymer Science (A) 3, page 45 (1965) a method for the synthesis of polyoxadiazoles from hydrazine sulfate and simple diacids such as terephthalic acid is disclosed. Other prior art references include the article by R. S. Jones, et al., in The Journal of Applied Polymer Science, Vol. 25, pages 315-321 (1980), British Patent Specification No. 1,455,776; Canadian Pat. No. 882,785 and the article by S. K. Varma, et al., in The Journal of Applied Polymer Science, Volume 26, pages 571-577 (1981).
The following Japanese patents further illustrate the prior art: Nos. J79,029,509-B42; J79,034,732-B47; J80,027,918-C34 and J50,037,778-W28 and U.S. Pat. No. 3,238,183.
None of the foregoing references contemplates polyoxadiazoles soluble in m-cresol and useful as coatings, molded objects and films. In the book Thermally Stable Polymers by P. E. Cassidy, Marcel Dekker, Inc., New York, 1980, p. 188, the author states that "fully aromatic polyoxadiazoles are soluble only in strong acids such as concentrated sulfuric or trifluoroacetic acid."
An object of this invention is to provide a polymer from 5-t-butylisophthalic acid (5-tBIA). A further object is to provide molded objects, coatings, films and fibers from the aforementioned polyoxadiazoles.
The reaction is conducted at a temperature of about 25.degree. to about 250.degree. C. The polyoxadiazole has an inherent viscosity measured in sulfuric acid at 25.degree. C. at a concentration of 0.5 g/dl of at least 2.0 and preferably about 2.1 to about 6.0 or higher.
The novel polyoxadiazole has the following repeating structure: ##STR1##
Fibers can be manufactured from the polymer in the following manner. The reaction solution, after completion of the polycondensation of the hydrazine sulfate with the appropriate diacid is cooled and mixed with sulfuric acid until a solution with the required viscosity is formed. The mixture is homogenized with stirring, and the resulting solution is filtered through an acid-proof fabric and deaerated under vacuum. The resulting spinning solution is formed into fibers using about a 0 to 55 percent aqueous solution of sulfuric acid as spinning batch. Non-washed, fresly formed fibers are oriented by stretching, for example, in air, or in a bath of about 0 to about 70 percent aqueous sulfuric acid, then washed with water to remove the sulfuric acid and dried. A useful fiber spinning method is disclosed by R. S. Jones, et al., The Journal of Applied Polymer Science, Vol. 25, 315-321 (1980).